The present invention relates to a cushioning fender assembly adapted to be mounted on one or both of the hull of a relatively large ship and a shore installation such as pier, wharf, quay, dock, float or the like structure for cushioning the impact of the ship against the shore installation.
Various types of elastically deformable fenders have long been used to cushion the impact of the ship against the shore installation for protecting both the boardside of the ship and such shore installation. By way of example, the British Patent No. 945,456, published on Jan. 2, 1964 discloses an elastically deformable fender of a construction comprising a hollow rubber tube of trapezium-shaped cross section with a fitting surface, a buffer surface opposite the fitting surface and a pair of support walls between the fitting and buffer surfaces, the section of the tube in a plane at right angles to the longitudinal axis of the tube having the approximate form of an isosceles trapezoid with its top forming said buffer surface, the bottom forming said fitting surface and the two lateral sides of equal length forming said supporting walls. This British patent specification further discloses that the fender of the above described construction can attain a maximum performance if the trapezium forming the cross sectional shape of the hollow rubber tube satisfies the following requirements:
A=H to 3H, B=0.2H to 0.8H, t=0.15H to 0.4H, and .theta.=45.degree. to 80.degree.
wherein H is the height as measured between the top and the bottom, A is the bottom width, B is the top width, t is the wall thickness of each of the support walls, and .theta. is the angle of each of the lateral sides relative to the bottom.
U.S. Pat. No. 3,418,815 discloses a fender of a construction comprising a hollow elastic tube similar to that disclosed in the above mentioned British patent specification, but has a rigid plate embedded in the buffer surface portion for optimum load-distribution both on the side of the ship and throughout the elastic material to produce improved energy-absorbing characteristics. The use of an additional rigid plate embedded in the fitting surface portion of the hollow elastic tube is also disclosed therein.
U.S. Pat. No. 3,418,816, patented on Dec. 31, 1968, discloses a fender assembly constituted by a plurality of fenders each being substantially identical with the disclosed in the above mentioned U.S. Pat. No. 3,418,815.
In addition, an elastically deformable fender of a construction having a substantially V-shaped cross section is well known. This known V-shaped fender comprises a pair of elongated support walls of equal width connected integrally at one side edge with each other by a buffer block, said buffer block having a flat buffer surface facing in a direction remote from fitting flanges which extend respectively from the other side edges of the associated support walls in a direction away from each other and in parallel to the plane of the buffer surface. This fender is of one-piece construction made of an elastic material such as rubber.
On the other hand, an elastic fender disclosed in the U.S. Pat. No. 3,820,495, patented on June 28, 1974, is considered an improved version of the above described V-sectioned fender in terms of the energy absorbability and is similar in construction to that V-sectioned fender except for a fluted groove and a fluted rib which are provided in the buffer block of the fender of the last mentioned U.S. patent. This last mentioned U.S. patent also discloses the use of rigid reinforcement plates each embedded in the corresponding fitting flange.
According to the last mentioned U.S. patent, the fluted rib extending lengthwise of the fender and protruding into a space between the supporting walls from the inside surface of the buffer block opposite to the buffer surface is so designed that, when the fender is extensively collapsed with the supporting walls outwardly buckled with respect to each other, said rib can abut on the shore installation to support the buffer block together with the buckled support walls for absorbing further shorck energy. On the other hand, the fluted groove extending lengthwise of the fender and defined in the buffer surface of the buffer block opposite to the fluted rib, thereby dividing the buffer surface into buffer areas one on each side of the fluted groove, is so designed that, as the fender is elastically collapsed, the buffer areas on respective sides of the fluted groove move in a direction close towards each other, while slip takes place between the boardside of the slip and each buffer area, thereby avoiding the possible outward expansion of of that portions of the fender where the support walls are integrally connected to the buffer block, so that the time at which each of the support walls starts its buckling movement under the influence of the impact applied thereto can be delayed.
The fender of the construction disclosed in the last mentioned U.S. patent can, in fact, exhibit an improved energy absorbability in view of the fact that the time at which each of the support walls starts its buckling movement can be delayed by the provision of the fluted groove. However, in practice, since the coefficient of friction between the buffer areas of the fender and the boardside of the ship is not always fixed and varies depending on the type of ships and/or the surface condition of the buffer areas, the movement of the buffer area on respective sides of the fluted groove in a direction close towards each other which takes place as the fender is collapsed by the application of a load thereto from the ship is not always stable and is likely to be facilitated where such frictional coefficient is low while to be retarded where it is high.
The Japanese Utility Model Laid-open Publication No. 49-34319, laid open to public inspection in 1974, the invention of which has been assigned to the same assignee of the present invention disclosed herein, discloses a fender assembly constituted by at least one pair of elastically deformable support columns, each being of a substantially I-shaped cross section, and a buffer member bridging or straddling these support columns. This fender assembly is advantageous in that not only can the possibility of damage to the boardside of the ship upon contact of the latter to the fender assembly be substantially eliminated, but also the fender assembly effectively serves to cushion the impact applied by a relatively large vessel.
However, all of the prior art fenders discussed hereinabove have a common disadvantage in that the energy absorbability is relatively low and, therefore, a relatively large amount of repulsive forces tends to be generated from the fender earlier than expected.